9.1 Properties of metals
- Syllabus
- 0620–2026–2027
- Topic
- 9.1
- Level
- —
Learning objectives
9.1.1Compare the general physical• Compare the general physical properties of metals and non-metals, (a) thermal conductivity (b) electrical conductivity (c) malleability and ductility (d) melting points and boiling points9.1.2General chemical properties of metals• Describe general chemical properties of metals, limited to their reactions with: (a) dilute acids (b) cold water and steam (c) oxygen
Compare metals and non-metals physically
| Physical property | Metals: general pattern | Non-metals: general pattern |
|---|---|---|
| thermal conductivity | good conductors of heat | poor conductors of heat |
| electrical conductivity | conduct when solid and molten | usually do not conduct |
| malleability | malleable: can be hammered or pressed into shape | brittle when solid |
| ductility | ductile: can be drawn into wires | not ductile |
| melting and boiling points | generally high | generally lower |
Use several properties together. A solid that conducts electricity and heat and can be bent or hammered without shattering is likely to be a metal; a brittle insulator is likely to be a non-metal.
Malleability concerns shaping sheets or other forms by hammering or pressing. Ductility concerns pulling a material into a wire; the terms are related but not interchangeable.
These are general patterns, not exception-free definitions. Graphite conducts electricity, and mercury is a liquid metal with a low melting point. Classify using the complete evidence supplied.
Describe the general reactions of metals
| Reagent | General products for a reacting metal | Example |
|---|---|---|
| dilute acid | salt + hydrogen | Zn + H₂SO₄ → ZnSO₄ + H₂ |
| cold water | metal hydroxide + hydrogen | 2Na + 2H₂O → 2NaOH + H₂ |
| steam | metal oxide + hydrogen | Mg + H₂O(g) → MgO + H₂ |
| oxygen | metal oxide | 2Mg + O₂ → 2MgO |
Hydrogen formation is shown by effervescence and is confirmed by a squeaky pop with a lighted splint. A metal may disappear as a salt solution forms in acid or as a hydroxide forms with cold water.
Distinguish the two water conditions: very reactive metals react with cold water to form hydroxides, while some less reactive metals react only with steam and form oxides. Reaction vigour depends on the metal's reactivity.
Acid reactions form salt and hydrogen—not salt and water. Steam reactions form an oxide, whereas cold-water reactions form a hydroxide. Metals below hydrogen in the reactivity series may not release hydrogen from dilute acids.